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Cited by 3 publications
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Multistage carcinogenesis in occupational cholangiocarcinoma: the impact of clonal expansion and risk estimation
Background Both mutation induction and clonal expansion of mutated cells cause cancer. The probability of cancer development depends on mutations, clonal growth rates, and carcinogenic mechanisms. A recent study showed cases of occupational cholangiocarcinomas that originate multifocally, with higher mutation burden levels than those in common cholangiocarcinomas. This study aimed to identify the effect of clonal expansion on and estimate the risk of occupational and common intrahepatic cholangiocarcinomas (ICCs) using a multistage model modified to include the effect of cell expansion at any carcinogenic stage. Methods The age-specific incidence of common ICC estimated from the Vital Statistics in Japan and the prognosis of ICC, and mutation frequencies of occupational and common ICC available from the previous report, were applied to a multistage model modified with cell proliferation effects. From the fittest model, the risk after exposure was estimated. Results The required number of stages for carcinogenesis was estimated to be three based on the incidences and mutation frequencies of occupational and common ICCs. Based on this estimation, the predicted incidence curve under the model was similar to that estimated from the ICC mortality rate, except for older adults. The model indicated a minor effect of clonal expansion on the observed occupational ICC risk. It predicted a rapid decrease in ICC risk after the cessation of occupational exposure, although the time of clinical detection of cancer after the exposure was affected by latency. The model predicted an increase in cancer risk in older adults caused by cell expansion and common background mutations. However, the risk in older adults was overestimated in the case of common ICC; this divergence could influence occupational ICC cases. Conclusions Three-stage ICC carcinogenesis has been proposed. The high mutation burden levels caused by occupational exposure led to an immediate incidence of cancer. After a long period of relatively low cancer risk, an increased risk in older adults was also predicted.
Multistage carcinogenesis in occupational cholangiocarcinoma: the impact of clonal expansion and risk estimation
Background Both mutation induction and clonal expansion of mutated cells cause cancer. The probability of cancer development depends on mutations, clonal growth rates, and carcinogenic mechanisms. A recent study showed cases of occupational cholangiocarcinomas that originate multifocally, with higher mutation burden levels than those in common cholangiocarcinomas. This study aimed to identify the effect of clonal expansion on and estimate the risk of occupational and common intrahepatic cholangiocarcinomas (ICCs) using a multistage model modified to include the effect of cell expansion at any carcinogenic stage. Methods The age-specific incidence of common ICC estimated from the Vital Statistics in Japan and the prognosis of ICC, and mutation frequencies of occupational and common ICC available from the previous report, were applied to a multistage model modified with cell proliferation effects. From the fittest model, the risk after exposure was estimated. Results The required number of stages for carcinogenesis was estimated to be three based on the incidences and mutation frequencies of occupational and common ICCs. Based on this estimation, the predicted incidence curve under the model was similar to that estimated from the ICC mortality rate, except for older adults. The model indicated a minor effect of clonal expansion on the observed occupational ICC risk. It predicted a rapid decrease in ICC risk after the cessation of occupational exposure, although the time of clinical detection of cancer after the exposure was affected by latency. The model predicted an increase in cancer risk in older adults caused by cell expansion and common background mutations. However, the risk in older adults was overestimated in the case of common ICC; this divergence could influence occupational ICC cases. Conclusions Three-stage ICC carcinogenesis has been proposed. The high mutation burden levels caused by occupational exposure led to an immediate incidence of cancer. After a long period of relatively low cancer risk, an increased risk in older adults was also predicted.
Oxidative Stress and Age-Related Tumors
Oxidative stress is the result of the imbalance between reactive oxygen and nitrogen species (RONS), which are produced by several endogenous and exogenous processes, and antioxidant defenses consisting of exogenous and endogenous molecules that protect biological systems from free radical toxicity. Oxidative stress is a major factor in the aging process, contributing to the accumulation of cellular damage over time. Oxidative damage to cellular biomolecules, leads to DNA alterations, lipid peroxidation, protein oxidation, and mitochondrial dysfunction resulting in cellular senescence, immune system and tissue dysfunctions, and increased susceptibility to age-related pathologies, such as inflammatory disorders, cardiovascular and neurodegenerative diseases, diabetes, and cancer. Oxidative stress-driven DNA damage and mutations, or methylation and histone modification, which alter gene expression, are key determinants of tumor initiation, angiogenesis, metastasis, and therapy resistance. Accumulation of genetic and epigenetic damage, to which oxidative stress contributes, eventually leads to unrestrained cell proliferation, the inhibition of cell differentiation, and the evasion of cell death, providing favorable conditions for tumorigenesis. Colorectal, breast, lung, prostate, and skin cancers are the most frequent aging-associated malignancies, and oxidative stress is implicated in their pathogenesis and biological behavior. Our aim is to shed light on the molecular and cellular mechanisms that link oxidative stress, aging, and cancers, highlighting the impact of both RONS and antioxidants, provided by diet and exercise, on cellular senescence, immunity, and development of an antitumor response. The dual role of ROS as physiological regulators of cell signaling responsible for cell damage and diseases, as well as its use for anti-tumor therapeutic purposes, will also be discussed. Managing oxidative stress is crucial for promoting healthy aging and reducing the risk of age-related tumors.
Elucidation of Factors Affecting the Age-Dependent Cancer Occurrence Rates
Cancer occurrence rates exhibit diverse age-related patterns, and understanding them may shed new and important light on the drivers of cancer evolution. This study systematically analyzes the age-dependent occurrence rates of 23 carcinoma types, focusing on their age-dependent distribution patterns, the determinants of peak occurrence ages, and the significant difference between the two genders. According to the SEER reports, these cancer types have two types of age-dependent occurrence rate (ADOR) distributions, with most having a unimodal distribution and a few having a bimodal distribution. Our modeling analyses have revealed that (1) the first type can be naturally and simply explained using two age-dependent parameters: the total number of stem cell divisions in an organ from birth to the current age and the availability levels of bloodborne growth factors specifically needed by the cancer (sub)type, and (2) for the second type, the first peak is due to viral infection, while the second peak can be explained as in (1) for each cancer type. Further analyses indicate that (i) the iron level in an organ makes the difference between the male and female cancer occurrence rates, and (ii) the levels of sex hormones are the key determinants in the onset age of multiple cancer types. This analysis deepens our understanding of the dynamics of cancer evolution shared by diverse cancer types and provides new insights that are useful for cancer prevention and therapeutic strategies, thereby addressing critical gaps in the current paradigm of oncological research.
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